Diesel fuel



Patented July 17, 1951 DIESEL FUEL Roy Sugimoto, Royal Oak, Mich., assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application July 28, 1950,

a Serial No. 176,543

4 Claims.

1 This invention relates to a composition of matter comprising Diesel fuel, a hydrocarbon fuel used in compression ignition engines, and an additive for improving properties of the fuel.

One of the fundamental advantages of the early form of the Diesel engine was its ability to satisfactorily burn almost any type of liquid fuel. However, the intensive development which has led to the modern high-speed Diesel engine has narrowed the range of suitable fuels to such a degree that present day fuels must meet many specifications. One of the most important specifications is ignition quality or the ease with which the fuel is ignited after it is injected into the cylinders of a'Diesel engine. This quality is measured in terms of cetane number which is defined as the percentage of n-cetane in a ncetane-a-methylnaphthalene blend which has an ignition quality comparable to the fuel in question. The use of fuels of poor quality results in starting difficulty and detonation, knocking, or rough running. The latter results in (1) increased engine maintenance, (2). reduced engine life, and (3) excessive vibrationand noise.

Straight-run distillates from parafiin-base crude oils are generally of high ignition quality.

Cracked distillates, or distillates from aromatic crudes are of inferior quality. Although most refiners have been and are able to supply adequate volumes of straight-run distillate or blends of straight-run with cracked distillate having a satisfactory ignition quality to meet the demand for Diesel fuel, it is becoming increasingly difiicult for them to do so. Furthermore, the rapidly expanding market for such fuels indicates that it will not be possible to continue to supply future demands without recourse to radically different refining techniques or the use of'fuel additives.

The use of cheap fuel additives to improve ignition quality (1) is more economical than the use of refining techniques, (2) permits refinery operation for low pour point and other desirable qualities, and (3) permits the use of more dense, higher heat content stocks than could otherwise be utilized due to their low ignition quality. The

Besides the ability to improve the cetane number of a fuel, an additive should be stable and have good blending properties with the fuel. The gem dinitroalkanes are deficient in respect to blending properties.

It is an object of this invention to provide a cetane number additive which decreases the ignition delay period of the fuel, which is stable,

and which blends readily with hydrocarbon Diesel distillates.

Among the gem-substituted dinitrocycloalkanes of my invention are 1,1-dinitrocyclohexane, 1,1- dinitro 3 methylcyclopentane, 1,1 dinitro-2- chlorocycloheptane, 4,4-dinitro-2-phenoxycyclohexanol, 1,1-dinitrodecalin, l-methyl-1.2,2-trinitrocyclohexane, 1,1,5 trinitrodecalin, 1,1 dinitrocyclopentane, 1,1,4,4-tetranitrocyclohexane, 1,1,3,3-tetranitrocyclopentane, and 1,1,2,2,-tetranitrocyclohexane.

Gem-dinitrocycloalkanes have a definite blending advantage over the dinitroparaflins. For example, 1,1-dinitrocyclohexane, one of my additives, is readily soluble in Diesel fuels, melts at 38 C. and when admixed with only a few per cent of a diluent, such as Diesel fuel, results in a liquid product which blends without difiiculty. On the other hand, 2,2-dinitropropane has a melting point of 53 C. and has limited solubility in distillate fuels, thereby limiting its use and impairing its effectiveness; Ll-dinitrocyclohexone is soluble in all proportions at temperatures slightly above its melting point and does not separate into two phases upon cooling to room temperature (25 C.).

dinitropropane (30 per cent in Diesel fuel) will On the other hand, 2,2-

' separate into twolayers when cooled below its use of such less expensive stocks permits greater melting point.

Dinitroparaffins are most economically prepared by a two-stage nitration of the corresponding paraffin. In the first stage, one nitro group is introduced by means of a vapor phase reaction at elevated temperature, and in the second stage, a

' second nitro group is introduced by a liquid phase reaction at a high temperature-and pressure. It is diflicult to obtain a high yield of a pure product and this results in an expensive product. For example, the mononitration of propane produces four products, namely l-nitropropane, 2- nitropropane, nitroethane and nitromethane. However, only one mononitration product is produced from cyclohexane, provided conditions are such as to prevent ring cleavage. Thus, high yields are obtained. To illustrate one way of making my Diesel additives, the following method for making 1,1-dinitrocyclohexane is given:

Twenty-five parts of l-nitro-l-nitrosocyclo- Catalytic cracked.

, in improving the ignition quality of a Diesel fuel is illustrated by comparing ignition qualities of a base distillate stock with a fuel blend comprising the distillate stock and one of my additives.

The ignition quality of the base stock and the fuel blend was determined by comparison with a standard reference fuel in a C. F. R. engine, using the ignition delay method, according to the method described in American Society of Testing Materials, volume 36, I, 418 (1936). 1,1-dinitrocyclohexane is chosen from among my additives to illustrate their effectiveness. Different blends were made with different types of base stock and the cetane number was measured as given in the following table:

Table Increase in Cetane N um- Fuel ber, Weight per cent Cetane Number ReflningProcess Crude Source 0.125 0.25, 0.5 1.0

Straight run Catalytic cracked. Straight run California West Texas.

Straight run It is to be noted that a large improvement in cetane number of the blend over the base stock was obtained in each case even when as little as 0.125 weight per cent of the additive was used. Similar results can be obtained when 1,1-dinitro- 3-methylcyclopentane, 1,1-dinitro-2-chlorocycloheptane, and 4,4-dinitro-2-phenoxycyclohexanol are substituted for 1,1-dinitrocyclohexane in the above tests.

My additives are considerably better than the dinitroalkanes from the viewpoint of stability and ease of blending, and are as good or better as ignition improvers. With some stocks my additives are distinctly better than the dinitroalkanes. For example, with a catalytically cracked distillate stock having a cetane number of 42, blends of 1,1-dinitrocyclohexane and 2,2-dinitropropane in amounts of 0.125, 0.25, 0.5 and 1.0 weight per cent resulted in a cetane improvement for 1,1- dinitrocyclohexane of 3.6, 6.3, 9.2 and 12.8, respectively, whereas for 2,2-dinitropropane the cetane number improvement was only 2.1, 3.8, 6.6, and 11.0, respectively. On a percentage improvement basis my additive increased the cetane number improvement for the different blends over the improvement obtained by a nitroparaflin' by 171 per cent, 166 per cent, 139 per cent and 116 per cent, respectively.

In general my additives are used in quantities between 0.05 and 2.0 per cent by weight of the base fuel.

I claim:

' 1. An improved Diesel fuel containing a minor proportion of a gem-dinitrocycloalkane containing from 5 to 10 carbon atoms in an amount suflicient to decrease the ignition delay period of the fuel.

. 2. An improvedv Diesel fuel containing a minor proportion of 1,1-dinitrocyclohexanein an amount suflicient to decrease the ignition delay period of the fuel.

3. A Diesel fuel as claimed in claim 1, containing between 0.05 and 2.0 percent by weight of the dinitrocycloalkane.

4. An improved Diesel fuel containing a minor proportion of 1,1:dinitro-3-methylcyclopentane in an amount sufilcient to decrease the ignition delay period of the fuel.

ROY SUGIMOTO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,387,279 McCracken Oct. 23, 1945 2,387,403 McCracken et a1. Oct. 23. 1945 7 2,465,984 Doumani et al Mar. 29, 1949 

1. AN IMPROVED DIESEL FUEL CONTAINING A MINOR PROPORTION OF A GEM-DINITROCYCLOALKANE CONTAINING FROM 5 TO 10 CARBON ATOMS IN AN AMOUNT SUFFICIENT TO DECREASE THE IGNITION DELAY PERIOD OF THE FUEL. 